使用接口和 EF Fluent API

Question

代码

我将向您展示代码，然后解释问题

接口

public interface IUser
{
    Guid ID { get; set; }
    string Name { get; set; }
    ICollection<IRole> Roles { get; set; }
}

public interface IRole
{
    Guid ID { get; set; }
    string Name { get; set; }
}

请注意，接口 IUser 定义了一个 IRole 类型的集合 Roles

实现

public class Role : IRole
{
    public Guid ID { get; set; }
    public string Name { get; set; }
}

public class User : IUser
{
    public Guid ID { get; set; }
    public string Name { get; set; }
    public ICollection<IRole> Roles { get; set; }
}

EF Fluent API 配置

public class RoleConfiguration : EntityTypeConfiguration<Role>
{
    public RoleConfiguration()
    {
        HasKey(p => p.ID)
            .Property(p => p.ID);

        Property(p => p.Name)
            .IsRequired()
            .HasMaxLength(70);
    }
}


public class UserConfiguration : EntityTypeConfiguration<User>
{
    public UserConfiguration()
    {
        HasKey(p => p.ID)
            .Property(p => p.ID)
                .IsRequired();

        Property(p => p.Name)
            .HasMaxLength(60)
            .IsRequired();

        HasMany(r => r.Roles).WithMany();
    }
}

请注意配置 EntityTypeConfiguration 其中 T 是实现而不是接口（EF 不允许将接口作为 T）

问题

#1 情况：

如果运行应用程序，则生成关系型模型，出现如下错误：

The navigation property 'Roles' is not a declared property on type 'User'. Verify that it has not been explicitly excluded from the model and that it is a valid navigation property.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 

Exception Details: System.InvalidOperationException: The navigation property 'Roles' is not a declared property on type 'User'. Verify that it has not been explicitly excluded from the model and that it is a valid navigation property.

Source Error: 


Line 58:         public IQueryable<Project> GetAll(int pageIndex, int pageSize, params Expression<Func<Project, object>>[] includeProperties)
Line 59:         {
Line 60:             return includeProperties.Aggregate<Expression<Func<Project, object>>,
Line 61:                 IQueryable<Project>>(Context.Projects, (current, includeProperty) => current.Include(includeProperty)).OrderBy(p => p.Name).Skip(pageIndex).Take(pageSize);
Line 62:         }

#2 情况：

如果注释掉 HasMany(r => r.Roles).WithMany(); 行，EF 将生成关系模型，其中 < code>User 和 Role （应该是多对多）

我相信这是因为 User 类中，有一个集合类型 ICollection< IRole>而不是 ICollection 类型。

问题

问题是，如何解决这个问题？ 如何映射集合public ICollection角色{获取;放;使用 Fluent API EF

Answer 1

CodeFirst 不支持映射接口。您需要更改它以引用 Role 具体类。

Answer 2

以下是我将如何实现您的接口，以解决贝蒂描述的问题。

public class Role : IRole
{
    public Guid ID { get; set; }
    public string Name { get; set; }
}

public class User : IUser
{
    public Guid ID { get; set; }
    public string Name { get; set; }

    // Explicit implementation of the IUser.Roles property.
    // Exists to satisfy the IUser interface but is not normally used.
    // Used only when the client code types this object the interface, IUser.
    // Otherwise ignored.
    ICollection<IRole> IUser.Roles 
    { 
        get { return this.Roles as ICollection<IRole>; }
        set { this.Roles = value as ICollection<Role>; }
    }

    // This property will be used in most cases.
    // Used when the client code types this object as the concrete type, User.
    public ICollection<Role> Roles { get; set; }
}